I'm having a similar issue, although in Chrome, where uploading a file to website is slowed down remarkably (43Mb file goes from about 5s to about 120s). Doing some debugging it seems that the slowdown is caused when the binary data is being passed into JSON.stringify. The particular code that's injected can be seen here
and there was a previous forum post about the same code 2 years ago
. That thread indicates that the issue was resolved in 4.1.40, but I'm using 4.24.0. The release notes for 4.1.40 say:
v4.1.40 - Feb 9th 2017 -- Chrome
Fixed: LastPass was interfering with the operation of a handful of sites when enabled.
Improved: More accurate prompts, now not prompted to save a site if security questions are submitted.
Fixed: Incorrect detection of username changes when login form is submitted.
There's also another similar current thread
about wordpress specifically.
Has this been raised as a support ticket by anyone? I'm just going to raise one just now.